molecular interaction study of some ortho and para...

ISSN: 0973-4945; CODEN ECJHAO

E-Journal of Chemistry

http://www.e-journals.net 2010, 7(1), 308-310

Molecular Interaction Study of some

ortho and para Substituted Anilines with 1-Octanol

M. S. MANJUNATHA* and J. SANNAPPA

Department of Physics, Yuvaraja’s College,

University of Mysore, Mysore-570024, Karnataka, India.

[email protected]

Received 27 May 2009; Accepted 20 July 2009

Abstract: Interactions between ortho and para substituents of anilines such as

chloroaniline, methylaniline and methoxyaniline with 1-octanol have been

studied in carbon tetrachloride. The most likely association of complex

between 1-octanol and substituents of anilines is 1:1 stoichiometric complex,

through hydroxyl group of 1-octanol and amine group of ortho and para

substituents of anilines. Interactions are studied on the bases of formation

constant and free energy changes. Formation constant of the complex has been

calculated using Nash method. The result shows that molecular interaction of

1-octanol as proton donor with methyl and chloride substitution of anilines in

ortho position is smaller than the para position substitution of anilines. The

results shows, the ability of acceptors is in the order p-methoxyaniline<o-chloro-

aniline<o–methylaniline<o–methoxyaniline <p–chloroaniline <p-methylaniline.

Keywords: Molecular interaction, Formation constant, Free energy change, Nash method.

Introduction

Molecular interaction study between associated and non associated liquid in an inert

media gives valuable information about solute-solvent and solute-solute interaction.

Spectroscopic technique is a power full tool to investigate the nature of molecular

complexes and hydrogen bonding. It is interesting subject to measure various

thermodynamic excess functions to obtain molecular interaction. A number of attempts to

develop a quantitatively accurate and physically meaning explanation of solvent induced

stretching vibration frequency shifts have been presented1-4

. Alcohols are industrially and

scientifically important organic compounds and their physical and chemical properties are

largely determined by their hydroxyl group. In the present work, an attempt has been

made to study the molecular association between free hydroxyl group of 1-octanol with

different amines group of ortho and para substitutes of acceptors in carbon tetra chloride

media using FTIR measurements.

Molecular Interaction Study 309

Experimental

A Nicolet Avatar 360 FTIR spectrometer with a resolution of ±1 cm-1

was used for this

study. Spectra were obtained at room temperature (25 0C) in the region of 4000 to 400 cm

-1.

The chemicals used were o-chloroaniline, o- methylaniline, o-methoxyaniline, p-chloroaniline,

p-methylaniline and p-methoxyaniline of Aldrich product used without further purification.

AR grade of 1-octanol and carbon tetrachloride were purified by standard procedure5, 6

and

redistilled before used.

Results and Discussion

The FTIR spectral data of o-chloroaniline, o-methylaniline, o-methoxyaniline, p-chloro-

aniline, p-methylaniline and p-methoxyanilinein 1-octanol are given in Table 1. The

proton acceptor of amines concentration was fixed and donor concentration varying

from 0.04 was carried out. From Table 1, it is noticed that the free amine stretching

band increases as the concentration of hydroxyl group increases and the intensity of

amine band decreases while half width slightly increases. The observation indicates the

1:1 complex formation between hydroxyl group of 1-octanol and the amine group of aniline

substituents. The FTIR spectra obtained using mixed solvent techniques indicates the

formation of complexes. It indicates the existence of 1:1 complex. Using Nash method7,

the equilibrium constant (k) for the 1:1 complex is calculated by using equation

]][[

][

BA

ABK =

(1)

Where [AB] is the concentration of the 1:1 complex and [A] and [B] are the initial

concentration of the proton donor and proton acceptor respectively. A graph was plotted

between 1][ −= AY and1

0

1

−

−=

a

aX

. Where a and 0a are the absorbance of the carbonyl band

of aniline substitutes in presence and absence of 1-octanol respectively. The intercept of the

graph in the ordinate yields K-1

. The changes in free energy8 of systems are calculated using

the equation

knlRTG −=∆ (2)

Where R represents universal gas constant, T represents absolute temperature and k

represents formation constant of the systems. The formation constant and free energy

changes values for ortho and para substituents of anilines with 1-octanol systems in the inert

solvent CCl4 are given in Table 1.

Table 1. Spectral data, formation constant and fee energy change of 1-octanol with ortho

and para substitution of aniline in CCl4 solvent at 309 K.

Systems

Proton donor Proton acceptor fγ in cm-1

k lit mol-1

- ∆G kcal mol-1

o-Chloroaniline 3494 75.00 2.678

o-Methoxyaniline 3485 138 3.056

o-Methylaniline 3479 148.38 3.101

p-Chloroaniline 3481 50.00 2.426

p- Methylaniline 3469 150 3.107

1-Octanol

p- Methoxyaniline 3459 195.23 3.271

310 M. S. MANJUNATHA et al.

An examination of Table 1 shows that the formation constant for the hydrogen bonded

complexes of ortho and para aniline with 1-octanol is in the order of

p-methoxyaniline < o-chloroaniline < o-methylaniline < o-methoxyaniline <p-chloroaniline. K

values for methyl substitute of aniline and chloride substitute of aniline in ortho position are

smaller then para substitution of aniline. This shows that molecular interaction has greater

steric hindrance involving free rotation of molecules. The complex formation is relatively

more in 1-octanol9. Because of steric hindrance, it is likely have greater probability of complex

formation due to head tail linkage10

. But for ortho position of methoxy substitute of aniline,

formation constant is higher then the para substitute of methoxy substitute of aniline. These

reveals that methoxy substitutes of aniline are comes under electron withdrawing groups.

The free energy change and formation constant vary with ortho and para substitute of

aniline with 1-octanol is suggests that the strength of intermolecular interaction occurs in the

ternary mixture. Proton acceptor ability is in the order p-methoxyaniline < o-chloroaniline <

o-methylaniline < o-methoxyaniline < p-chloroaniline < p-methoxyaniline.

Conclusion

The formation constant and free energy change of ortho and para substitute of amines with

1-octanol in ccl4 are carried out. From this study one may conclude that the strength of

intermolecular bond formed between the ortho and para substitute of amines and 1-octanol

is shown that the tendency of molecular interaction is relatively more in para substitute than

that of ortho substitute of anilines.

References

1. Navarro R, Hernanz A and Bratu I, J Mol Struct., 1995, 348, 253.

2. Symons M C R, Chem Soc Rev., 1983, 12, 1.

3. Bratu I, Grecu R, Constantinescu R and Iliescu T, Spectrochim Acta Part A., 1998,

54A, 501.

4. Streck R and Barnes A J, Spectrochim Acta A., 1999, 55(5), 1049.

5. Hernandez B, Gavira-Vallejo J M, Navarro R and Hernanz A, J Mol Struct., 2001,

565, 259.

6. Riddick J R and Bunger W B, Organic Sovents, Wiley Intersciences, New York, 1970.

7. Nash C P, J Phys Chem., 1960, 64, 632.

8. Vinogradov C R H, Hydrogen Bonding, van Nostrand Reinhold Company, New

York, 1971.

9. Chandra A K and Basu S, Trans Frarday Soc., 1960, 56, 632.

10. Das J K, Dash D K, Acharya S and Swain B B, Jpn J Appl Phys., 1996, 35, 453.

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